Servo-brake



F. ATFIIMON -July 28,' 1931.

SERVO BRAKE Urignal Filed Sept. 30, 1927 2 Sheets-Sheet l lll lllH 4 lli July 28, 1931. F. ATHIMON 1,816,067

SERVO BRAKE Original Filed Sept. 30, 1927 2 Sheets-Sheet 2 Patented July 28, 1931 ERANCIS ATH-IMON,

PATENT OFFICE or PARIS, FRANCE sERvo-BRAKE Original rapplication rfiled September 30, 1927, Serial No. 223,168, and in France October 6, 1926. Divided and ythis application `led'tctober 279, 1928. Serial No. 315,801.

The present invention'which is a division as a centre. Upon the axle 34 are mounted of my copending application No. 223,168

iled September 30, 1927, now patent No.y

1,727,742 of September 10, 1929, relates to improvements in the brake control mechanism of the type described in the above mentioned patent application.

An object of the invention is to provide:

means whereby the maximum braking action maybeI obtained Jorvariable strokes of the control member operated by the driver of thef'vehicle. f

Another object of: theinvention is to provide means whereby variable `efforts may be exerted on the brakes for a same expansion strokecofthe relay springfwhich contributes with the effort exerted by the driver for applying the brakes.

Further vobjects and characteristic features et the invention will be apparent from the following description of an embodiment showmby way of example in the accompanying drawings, in which:

isa vertical section. on the line 1,-1 of Figure 3.

Fig. 2 is afvertical' cross section on the line 2 2 of Fig. l.

Fig. 3'is.a plan viewof the apparatus. with the cover removed.

Fig. 4 is a horizontal section on the line- 4-4 of'Fig. 2.y f Y The vapparatus is placed in. a casing 4 between theV lrod2 2rleading to the brake pedal and the rod 3 leading to thev brake. To the rod 2 is.V pilvoted the lever 16 pivoted at 1,4 tothe lever 27, which is pivotally mounted on the axle 28. The lever 27 comprises at the lower part a cylindrical portion L b which is concentric with the axis 28, and an eccentric ramp 29 extending from b to c. By.y means .of said cylindrical portion and saidl ramp, the lever 27 bears -upon the roller 301 which is mounted by'ball-bearings on theshaft 34 carried by two parallel levers 31 pivoted on the axle 32 which is mounted in two respective holes in twoplates 35 secured tothe casing 4; said plates are pierced with various holes 36 having thesame diameter as the axle 32 and whose centres are situated on an arc of a circle having the axis 34 on the respective sides of the roller 30, two rollers 37 of a somewhat large diameter;v said rollers make contact with. a lever 38. which comprises two vertical lugs 39-40 and is pivoted on an axle 41 secured to the casing. By means of the screw 42, the slide 43 is movable between the lugs39' and 40, and itV makes contact with the plate springy 33 secured to the casing 4 at 44. rlhe lower end of the lever 16 is slotted in order to limit the motion of the lever 16 with respect to. the lever 27 by coacting with the stud 17 on the lever 27.

The operation. is as `follows By the action of the spring 33, the lever` 38 is subjected to a couple C1 whose magnitude can be changed, by means of the slide 43', by the displacementof the point ot application of the force. Variable eflortsmay thus be applied on the lever 27 for a same' expansion of the spring 33.. The lever 38 acts upon the rollers 37 which are subjected to a couple C2 by which the rollers and the levers 31 are pivoted on the axis 32 and to a tangential force by which the rollers 37 are rotated on their axis. The couple C2'is manifested by a force F perpendicular to thesurface ofcontact between the roller 30 and the lever 27; said force produces a couple rotating the lever 27 when it does not pass through the axis 28.

In all positions of the lever 27 between the inoperative position (on the right of the position shown in Figure 1) and the position shown in Figure 1, the point of application of' the force is situated between a and b. This force passes through the axis 28 and has no effect on the rod 3 but when the lever 27 is further moved to the left (Figure 1), the direction oi' the force passes through the centres of curvature of the curve b-c which difler from the axis 28, so that the lever 27 is subjected to a. couple whose moment increases from Zero to a maximumv value which is attained at the end of the stroke. In this position, the spring 33' is somewhat expanded, but is far from its maximum eX- pansion. For the maximum braking, ify T kgs. traction are required for the maximum brakes will preponderate and will give the` brake pressure, (T-) kgs. will be balancedl by the action of the spi'ing, and there will remain t kgs. to be furnished by the driver. Since the traction Yof the rod 3 increases with the displacement of the lever 27 to the left and sincey the action ofthe spring is proportional to this displacement, the same proportion between the aid furnished by the spring and the effortY to be exerted bv the driver will be maintained throughoutl the entire braking stroke. Then the driverv ceases his effort, the elastic tension rof the spring the tension which it had at the start. According tothe position of the axis 32, l may advance or delay the time at which the roller 37 isbrought into contact withthe point C of the curve of c coriespondingYV tothe maximum braking. lt willthtis be ypossible to vary the stroke of the rod 2 and consequently of the pedal or operating lever for obtaining the maximum braking.

TheY apparatus herein described can be completedto advantage by the device for taking up the wear as in my copending application 223,168. Said device chiefly comprises a ratchet nut which is mounted on the end offthe rod 3, and a'pawl 18 which is secured by the screw 19 to the lever 27; said pawl is provided with a reaction spring 18b and it comprises an arm .18 of circular arc shape having a bevelled edge which e makes contact with the end of an angular f lever 20 provided with a ramp 50 and with a locking notch 51 and pivotally mounted atk 22. The lever 20 is actuated on the portion Y 2Oa by a rod 23 secured tothe lever 16. A spring 24 is connected at one end with an extension of the lever 16 and at the other end with the lever 27. During the inoperative stroke of the said rod-and-link gear, the lever 27, the spring 24, 'the lever 16 and the rod 23 are bodily pivoted as a Whole about the axle 28, and the lower end of said rod 23 slides on the portion 20EL of the lever 20 without swinging said lever. When the braking action begins, the lever 16 rotates for a moment about the axle 14 until the right side of the slotted end ofthe lever 16 bears on the stud 17.k The rod 23 presses against the portion 20a of the lever 20 and causes said lever to turn about the axle 22. l/Vhen the rod-and-link gear is properly ad- Vjusted, the ramp presses on the bevel part further about the axle 28 during the irioperative stroke, so that the rod 23 will slide on a greater dista-nce on the portion 20a. When the braking action begins, the rod 23 rotating about the axlev 14 slides on the remaining `portion of the projection 20 and rotates the lever 20, butsaid remaining portion being insuflicient, the rod 23 falls beyond saidyprojec-tion before. the upper branch of the lever 2O has brought the locking notch 51 opposite the bevel of the arm 18a. VThe pawl 18-falls thus again on the ratchet nut, rotates with the lever 27, engagesV the following tooth ofthe ratchet nut 1,5, and during the return stroke of the brakes to the inoperative position, screws the ratchet nut for one tooth, thus taking up the excessive play.

flbviously, the said invention is not limited to the .details of construction herein described and represented by way of example.

Having now describedmyinvention, what vIclaim as new and desire to secure by Letters Patent is: f Y

1. ln a brake control mechanism,.the combination of a control member adapted to be moved by an operator, a reacting member, a stationary pivot, a lconnectingememrber pivotedto said control member, tosaid reacting member andV to said stationary pivot, a cam surface on said connecting member, a pivoting axle, a rocking arm pivoted on said pivoting axle and adapted to bear on said cam surface, a spring adapted to urge said rocking'arm against said cam surface and means adapted to hold said pivoting axle in different positions, whereby said rocking arm is adapted to bear on variable portions of saidicam for a given position of said control member.

2. In a-brake control mechanism,the-com bination of a control member adapted to be lmoved by an operator, a reactingmember,

a* stationary pivot, a connecting member pivoted to said control member, to said reacting member and to said stationaryv pivot, a cam surface on saidA connecting member, a pivoting axle, .a rock-ing arm pivoted on said pivoting axle and adapted to bear on said cam surface, a stationary stud, av lever pivoted on said stationary studand adapted to bear on said rocking arm, a contact piece adjustably mounted fon said lever and a spring bearing on said Contact piece and adapted to urge said lever against said rockingarm and said rocking arm against said cam surface, whereby variable efforts may be exerted on said rocking arm and on said cam surface for a same expansion stroke of said4 spring.

3. ln a brake control-mechanism, the combination of a control member adapted to be moved by an operator, a reacting member, a stationary pivot, a connecting member pivoted to said control member,to said reacting to bear on said rocking arm, a screw carried byv said pivting lever, a slide adjustably mounted on said screw and a spring bear-l ing on said slide and adapted to urge said lever against said rocking arm and said rocking arm against said cam surface, whereby variable e'orts may be exerted on `said rocking arm and on ksaid cam surface for a same expansion stroke of said spring.

4. In a brake Control mechanism, the combination of a easing, a stationary pvot in said casing, a connecting member in said easing pivoted 0n said stationary pivot, a cam surface on said connecting member, a

control member pivoted on Said connecting member, a reacting member pivoted to said 'connecting member, a flat tensioned spring disposed on the inner side of said casing,

and means interposed between said spring and said Vcam surface and adapted to transmit theJ tension of said spring to said conlneeting member.

In testimonyvvhereof I have signed my name to this specification. FRANCIS ATHIMON. 

